The prior art for gluing fragments and scales of wood for producing semi-finished wood panels includes the use of a special resin bonder machine which the wood chips are directed to, and in which the chips are mixed with the glue injected into the machine by special injectors.
The above-described machine is essentially constituted by a large cylindrical drum rotated about a horizontal axis thereof and internally provided with elements or similar components applied on the perimeter surfaces thereof in order to draw the wood fragments in rotation and to improve mixing.
These machines obviously have to be large, and need frequent and laborious maintenance and cleaning operations in order for the materials that deposit on the internal surfaces thereof to be removed, as these material accumulate between the elements and cause a progressive reduction of the mixing efficiency of the machine; there are also large masses of chip and glue to be detached and removed. Also, it is not possible to control the correct distribution of the glue throughout the wood materials and adjust the sprayers accordingly while the machine is operating, without first stopping the production process.
The main aim of the present invention is to provide a process for gluing scales, fragments and chips of wood, in which the distribution of the glue is optimised and the use of resin bonding machines of the above-described types is avoided.
A further aim of the invention is to provide an apparatus for gluing wood chips, scales and fragments in general, which obviates the above-described drawbacks in the prior art.
The above-cited aims and others besides are all attained with a process for gluing wood scales, fragments and chips in general, which process comprises:                a continuous weighing stage of the chips which the glue is to be distributed in;        a spraying stage of the glue on the wood chips, in a quantity which is proportional to the calculated weight, together with compressed air and/or steam in order to soften the wood chip, making the wood chip less fragile for the subsequent mixing stage;        a material mixing stage using special machines made in such a way as to obtain an optimal distribution of the glue on the wood chips while at the same time preventing breakage of the chips and the adhesion of the above material to the various components of the machines, or in any case to make the machines easy to maintain.        
The glue spraying operation is done using special injectors positioned at a hopper located at the outlet of the continuous weighing apparatus.
The process can advantageously include a stage in which the glue is injected under pressure, together with compressed air and/or water steam, using the same injectors or other dedicated injectors.
An apparatus for gluing wood scales, fragments and chips in general comprises means for continuously weighing the wood chips on exit thereof from relative storage tanks; at least a hopper provided with injectors of glue, and/or steam, the injectors being connected to relative pressurised supply plants; at least a resin bonder machine for completing the gluing process by mechanical mixing of the material.
The resin bonding machine comprises a cylindrical body in which two oppositely-pitched helices are rotated by a central horizontal shaft of the machine; the various components of the machine are internally cooled in order to prevent adhesion of the material thereon; the body can be opened to enable the maintenance operations of the machine.
The above-described characteristics clearly demonstrate the advantages of the machine of the invention with respect to prior-art resin bonders; in particular the machine offers advantages in reliability and practicality of use.